1. Field of the Invention
The present invention relates to a decorative sheet for use to decorate a formed product and also relates to a formed product decorated with such a decorative sheet and to a transportation apparatus including such a formed product.
2. Description of the Related Art
Various formed products are used as interior and exterior members for a transportation apparatus such as a car. Recently, it was proposed that a decorative sheet such as that disclosed in Japanese Laid-Open Patent Publication No. 2005-153351 be attached to the surface of a formed product as a technique of decorating various types of formed products.
FIG. 11 shows an example of the decorative sheet. The decorative sheet 110 shown in FIG. 11 includes a base member 1 of a resin material and a decoration layer 3 formed on the principal surface 1a of the base member 1 by printing a pattern on that surface 1a with ink, for example. The ink includes a resin material and a pigment that is dispersed in the resin material. By attaching this decorative sheet 110 to the surface of the body 121 of a formed product in the order shown in FIGS. 12A, 12B and 12C with an adhesive 8 applied on the decoration layer 3, a formed product 120 with a decorated surface can be obtained.
The formed product 121 shown in FIG. 12A includes a hemispherical (cuplike) raised portion 121a and therefore has a rugged surface. For that reason, the decorative sheet 110 being attached is stretched so as to follow such ruggedness perfectly. To stretch the decorative sheet 110 just as intended, the decorative sheet 110 is typically heated and softened before being attached. Japanese Laid-Open Patent Publication No. 2005-153351, also discloses a vacuum forming system for decorating a formed product with the decorative sheet 110.
A formed product with a decorative sheet can be recycled more easily than a formed product with a painted surface. In addition, a decorated product can have a different type of fine appearance from that of a painted product. That is why a decorative sheet contributes to improving the appearance of formed products noticeably. For these reasons, a method using a decorative sheet is very useful.
Meanwhile, a decoration technique using a luminous pigment has attracted a lot of attention recently. The luminous pigment has a property of absorbing and storing sunlight, light radiated from a fluorescent lamp, or any other type of energy and gradually releasing the energy and producing luminescence either at night or in the dark. By utilizing this property of the luminous pigment, the product can be decorated uniquely so as to give the user quite a different impression than simple painting.
Japanese Laid-Open Patent Publication No. 2003-25793 discloses a transfer film for decorating a wall, a piece of furniture, a consumer electronic product, or any other object with a luminous pigment. FIG. 13 illustrates a transfer film 210 as disclosed in Japanese Laid-Open Patent Publication No. 2003-25793, supra.
As shown in FIG. 13, the transfer film 210 includes, on a base member film 211 of polyester, a peel processing layer 212 that provides a release property to the base member film 211, a protective layer 213 made of a UV curable resin, and a luminescent coating layer 214 formed by dispersing a luminous pigment in a thermosetting epoxy resin. These layers 212, 213 and 214 are stacked in this order on the base member film 211. An aluminum evaporated layer 215 and an adhesive layer 216 are further deposited on the luminescent coating layer 214.
As shown in FIG. 14, by peeling the base member film 211 and the peel processing layer 212 after this transfer film 210 has been bonded to an object 221, the stack of the adhesive layer 216, the aluminum evaporated layer 215, the luminescent coating layer 214 and the protective layer 213 is transferred onto the object 221. As can be seen from the arrangement of the respective layers shown in FIG. 14, the protective layer 213 is arranged so as to protect the luminescent coating layer 214 after the film 210 has been transferred.
The transfer film disclosed in Japanese Laid-Open Patent Publication No. 2003-25793 is designed just for the purpose of transferring the luminescent coating layer. That is to say, the transfer film cannot be stretched while being attached as disclosed in Japanese Laid-Open Patent Publication No. 2005-153351. In other words, the transfer film cannot be attached so as to fit the surface shape of the formed product perfectly.
Also, if the luminous pigment were simply added to the decoration layer of the decorative sheet disclosed in Japanese Laid-Open Patent Publication No. 2005-153351, then the decoration layer could crack while the decorative sheet is being attached and might ruin the fine appearance of the sheet. This is because if the luminous pigment were added to the decoration layer, the decoration layer could not be stretched so easily as to keep up the stretch of the decorative sheet being attached or the shrinkage of the decorative sheet that has cooled down after that. Such cracking can be reduced to a certain degree by reducing the thickness of the decoration layer. If the decoration layer were thinned, however, the amount of the luminous pigment included in the decoration layer would decrease too much to make the decoration layer produce luminescence with a sufficiently high intensity for a long time.
Such a problem would arise not just when the luminous pigment is added to the decoration layer but also when the decoration layer may include a certain amount of pigment (e.g., when either a metallic pigment or a glass pigment is added to the decoration layer). If a decoration layer is formed using ink in which a metallic pigment is dispersed in a resin material, then the resultant decorative sheet can have a metallic color, which gives the product a great-looking metallic appearance, due to the metallic gloss of the metallic pigment. Also, if a decoration layer is formed using a glass pigment (i.e., a ceramic pigment), then the resultant decorative sheet can have a lame-like glittering appearance.
Nevertheless, if such a metallic pigment or glass pigment is added to the decoration layer, the decoration layer could also lose its stretchability so much so that it may crack from time to time while the decorative sheet is being attached. Such cracking can be reduced to a certain degree by reducing the thickness of the decoration layer. If the decoration layer were thinned, however, the amount of the metallic or glass pigment included in the decoration layer would decrease too much to achieve the expected decoration effect. Furthermore, even if the decoration layer includes only a normal coloring pigment, the decoration layer may also lose its stretchability so as to crack in some cases.